OzFclass

Anyone experienced a tight throat with this cartridge?
I'm getting pressure signs on a new barrel with 27gn AR2206H and 28gn AR2208. Bullet used is 105gn Hornady A-Max.

Norm,

Not the most likely cause, but make sure cases are trimmed to length.

What are the pressure signs BTW? I know that some primers e.g. Rem 7.5 (?) are very soft.

Alan

Hi Norm.
Im loading 30.3 grns 2208 behind berger 105s. Using lapua cases and cci br4 primers. No signs of excess pressure. .267 neck bushing die.
Shot a .150 5 shot group with it last weekend. Hope this helps

Norm,

What are you identifying as pressure signs?

If you're using virgin brass or brass that's sized under the length of your chamber, your primers are likely to be flattened due to them backing & expanding out during the ignition stage, then being squeezed into the pocket when the case expands to fill the chamber.

John

Looks like I found the problem.
Short free bore mixed with long projectiles.
Seems the chamber was cut with a "Varmint" reamer with a lead of 0.070". This puts the 105 gn A-Max way down into the cartridge.

So I will have to look for a shorter bullet for shooting out to 600 yards, any suggestions?

Throat it out.

Hi Norm. How about the 95 grain Berger. Might give you a bit more room.

Hi Norm,

Just a quick note, I see that you are using 2206 and 2208. I find that 2209 works extremely well in my 6mm BRX. You may wish to play with some of that powder, and see how well it fits in your cases.


Cheers,

Bartman007

I got hold of some 105gn Berger VLD (hunting) projectiles today and they have a much shorter bearing surface and a secant ogive.
This permitted me to seat these projectiles out further and load in another 4.5 grains of powder before I saw any pressure signs.
ie from 25gn to 29.5gn.
This got me 400 fps extra velocity!

Now the throat is a problem for sure so a new throating reamer is on order.